libdaemon: ensure threads are reaped before checking shutdown

Since we are checking _shutdown_requested - we expect all threads
are finished - that is currently checked only by checking ->next ptr
being NULL - so this can be NULL only when _reap() function clears
out all already finished threads.

I'm finding this design quite problematic in its core - but as a
'trivial hotfix' - lets _reap() linked list before check for signal.

There is likely a large potentical for few races - but the windows is
very very small - since lvmetad has been already purged from upstream,
lets go with this hotfix.

libdaemon/server/daemon-server.c

@@ -655,6 +655,7 @@ void daemon_start(daemon_state s)
 		FD_ZERO(&in);
 		FD_SET(s.socket_fd, &in);
 
+		_reap(s, 0);
 		sigprocmask(SIG_SETMASK, &new_set, NULL);
 		if (_shutdown_requested && !s.threads->next) {
 			sigprocmask(SIG_SETMASK, &old_set, NULL);